On Saturday, Trump said his talks with Kim could end with no agreement or they could be "the greatest deal for the world".
Mr Chung expressed thanks for China's role at a meeting earlier with China's top diplomat, State Councillor Yang Jiechi.
In Geneva, the United Nations investigator on North Korea told the world body's Human Rights Council that any progress in the nuclear and security dialogue must be accompanied by talks on human rights violations, including political prison camps.
Trump administration officials have said there will be no more conditions imposed on North Korea before a meeting of the two nations' leaders. But he says the USA does expect to hear directly from Pyongyang.
Sanders said that the maximum pressure campaign on North Korea is working.
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The Swiss foreign ministry has said the country is ready to facilitate talks between North Korea and the United States, and is in contact with both sides.
In an unexpected move last week, Trump agreed to hold a first-ever meeting with Kim, which South Korea said would take place by the end of May after a North-South summit in April. They also say the North could even offer to reduce the amount of nuclear materials it has saved for making nuclear weapons.
As Stanford political scientist Scott Sagan summarizes, "States will seek to develop nuclear weapons when they face a significant military threat to their security that can not be met through alternative means; if they do not face such threats, they willingly remain non-nuclear states."Kim is in this sense a rational actor in pursuit of regime survival and dynasty preservation, perceiving nukes as his sole effective tool". "The secretary has not spoken to the North Koreans". A dozen White House officials including U.S. Vice President Mike Pence and Chief of Staff John Kelly were also present, along with McMaster, Mattis, and Haspel. "I don't think it's that unusual" that we haven't heard from the North Koreans yet.
JOINT SECURITY AREA, PANMUNJOM One of the most likely sites being discussed is the Joint Security Area in Panmunjom that straddles the Military Demarcation Line between North and South Korea. Global sanctions against North Korea must be maintained until the complete, verifiable and irreversible scrapping of North Korea's nuclear weapons program is achieved.
"There is a possibility no nuclear submarines will be coming either", the source added.
Brian Padden reported this story for VOANews. Mario Ritter adapted the report for Learning English. George Grow was the editor. But Trump responded: "No, it's very positive ... no, after the meeting you may do that, but now we have to be very nice because let's see what happens, let's see what happens". Write to us in the Comments section, and visit our Facebook page.